• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.46-50
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• 2007

The nuclear power plant's turbine-generator system had been suffered form some problems, such as high shaft vibration, generator casing crack, stator coil water leakage, high $H_2$ gas consumption rate. Those kinds of problems were related to high vibration. So nuclear plant decided to replace generator in order to reduce rotor high vibration and high thermal sensitivity. A series of effort to reduce turbine-generator vibration was carried out as followings, first of all, replacement of generator, analysis of turbine-generator vibration, LP B rotor shop balancing, improvement of LP B/Gen coupling run-out, improvement of Generator basement and field balancing. Finally the nuclear turbine-generator's shaft vibration was reduced below $60{\mu}m$ from over $200{\mu}m$ which is very excellent vibration in nuclear turbine-generator in Korea.

• 대한기계학회논문집A
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• 제30권8호
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• pp.1016-1023
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• 2006

When one opens the door of a microwave oven during its operation, twisting deformation of the door occurs, which may cause leakage of microwave through the gap between the door and the front plate. A numerical optimization is implemented to minimize the gap by maximizing twisting stiffness of the door of the oven. Design variables are deformed, which describe the shape of the bead in the horizontal and vertical flanges of the door frame. To minimize the twisting deformation, Two optimal design problems to find shapes of the bead in the flange are established. The problems are solved by a numerical optimization technique, their results being evaluated.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2003년도 총회 및 춘계학술발표회
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• pp.352-355
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• 2003

27 passive systems in 21 mines constructed by The Coal Industry Promotion Board since 1996 were investigated to evaluate the treatment efficiency of systems and find problems in each system, which will eventually lead to the improvement or suggesting the alternative method of the passive treatment system. Problems in operation include overflow, leakage, inefficiency and unusablness. The efficiency of systems which has been evaluated by metal(Fe) removal rate and/or by acidity removal rate do not reflect the poor removal rate of S $O_4$$^{2-}$. Especially high concentration of S $O_4$$^{2-}$ and high COD in the beginning of the operation would decrease the bacteria activity due to the lack of the nutrition. To solve the problem of overflow the upflow-type SAPS is being considered.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권8호
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• pp.423-429
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• 2006

Recently, the high frequency isolated boost DC/DC converter has been widely used for the PCS (Power Conditioning System) system because of its small size and low cost. However, the high frequency isolated boost DC/DC converters applied the conventional voltage-fed converter and current-fed converter have the problems such as the high conduction losses and the surge voltage due to the high circulating current and the leakage inductance, respectively. To overcome this problems, in this paper the secondary LLC resonant converter is proposed, and the experimental results of the secondary LLC series resonant converter for boost DC/DC converter are verified on the simulation based on the theoretical analysis and the 700W experimental prototype.

• 전력전자학회논문지
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• 제21권1호
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• pp.27-33
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• 2016

A pulse-width modulation (PWM) method for common mode noise reduction in a PWM inverter connected to a single-phase grid is proposed in this study. The extensively used conventional switching method may experience common mode voltage problems, which generate current leakage and electromagnetic induction problems. In the proposed switching method, the neutral point of the output voltage is always fixed at both ends of the input voltage to reduce common mode noise. The validity of the proposed method is proven through simulation and experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.262-268
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• 2001

Remarkable progress has been performed in power electronics, using high frequency switching based on the improvement of power semi-conductor devices. In the other hands, it gives us serious problems, such as, insulation, increasing of the high frequency leakage current, and electric corrosion of bearing in the loaded motors driven by inverters using high frequency switching. To improve these problems, many researches have made especially on the application of soft switching technologies. From this point of view IEE-Japan had started the research groups on soft-switching technology 1997 and 1999. This paper is a survey based on the discussion in this research group with results of ARCP inverter applied for 210kVA power supply.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1059-1061
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• 2005

The bushing currently applied to pole-mounted type loadbreak switch has porcelain bushing which is connected with the mold cone. This type has potential problems of uncertainty of sealing of the interface part and gas leakage on the connected part between bushing and switch tank due to the weight of the porcelain. The Composite Bushing can solve these problems and also the secondary problem of the potential accident owing to the fragment of the porcelain bushing in breakage due to the outer impact.

• ETRI Journal
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• 제44권2호
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• pp.339-345
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• 2022

This article presents an investigation of the effects on a grounding system of wireless power transfer (WPT) when transmitting over relatively far distances, that is, up to 1.25 m. Conventional two-coil WPT systems are sufficiently commercialized in strong coupling range, but it is important to accomplish the long-range WPT in weak coupling range for further various applications. This system depends on the coupling effect between the two coils that the grounds of the transmitting and receiving coils should be completely separated. However, when evaluating the performance of two-coil systems with the instrument consisting of two ports and one common ground, undesirable problems occur in weak coupling ranges, for example, obtaining disagreeable transmission efficiency and degrading system stability/reliability. We investigate the problems of the leakage power from common ground systems and provide a practical solution to obtain a reliable WPT system by using an isolation transformer. The usefulness of this approach is that it is possible to achieve the stability of the system with relatively far transmitting distances and to determine the exact transmission efficiency.

• Journal of Korean Neurosurgical Society
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• 제38권4호
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• pp.259-264
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• 2005

Objective : The vertebroplasty is an excellent procedure in spine compression fracture, but there are some problems such as cement leakage and difficulties in bone biopsy. Recently, the osteoplasty system is developed to solve these problems, so we will report the usefulness of the osteoplasty system. Methods : From January 2003 to November 2003, there are 9patients with simple osteoporotic spine compression fracture, 2 compression fracture patients combined with suspicious spinal metastasis, 1patient with suspicious primary bone tumor, and 2patient with infection on spine. All patients were treated using the osteoplasty system. Results : All 11 compression fracture patients were relived the back pain after the osteoplasty and there is no complication. The bone biopsies in 3 suspicious cancer patients were also effectively performed using the osteoplasty system; negative result in 2patients and positive result in 1patient. The culture result of spontaneous discitis was no growth for 48hours. The spine tuberculosis was confirm using the osteoplasty system. Conclusion : The osteoplasty system has distinguished advantages in comparison with the vertebroplasty. That is, the risk of cement leakage is lower than vertebroplasty because of low pressure delivery system. And we can obtain the specimen effectively in bone biopsy because of large cannula. In conclusion, we emphasize that the osteoplasty system is a more useful procedure in spine compression fracture especially in the patient needed bone biopsy for diagnosis.

• 한국전자파학회논문지
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• 제15권3호
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• pp.271-277
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• 2004

초고주파 및 밀리미터파 통신 시스템의 집적회로 및 실장 기술로서 CPW기반의 전송선로를 갖는 MMIC 개발이 크게 증가하고 있으나, 실장시 패키지에서 발생되는 기생공진 현상으로 인해 그 성능이 크게 저하될 수 있다. 이런 기생 공진 현상을 억제시키기 위하여 도핑된 lossy 실리콘 웨이퍼를 칩 캐리어로 사용하고, HRS wafer를 사용하여 표면 및 벌크 MEMS 공정이 가능한 실리콘 MEMS 패키지가 해석적으로 제안되었다. 제안된 구조를 제작하여 세 가지의 칩 캐리어(conductor-back metal, 15 Ω$.$cm lossy Si, 15 ㏀$.$cm HRS)위에서 측정하여 실리콘 MEMS 패키지의 특성을 확인하였다. 제안된 실리콘 MEMS 패키지는 15 Ω$.$cm lossy 실리콘 칩 캐리어를 사용하여, 기생 공진 현상을 효과적으로 억제시킬 수 있었다. 전체 패키지에서 중앙의 GaAs CPW 패턴을 de-embedding하여 순수한 CPW MMIC 용의 실리콘 MEMS 패키지는 40 ㎓에서 삽입 손실은 - 2.0 ㏈이며, 전력 손실은 - 7.5 ㏈의 결과를 얻었다.